There is a continuing effort to improve absorbent products, such as diapers, sanitary napkins, wound dressings, bandages, incontinent pads and the like, that absorb body fluids and contain them well without leakage. Generally, it is preferred that such absorbent products be soft and readily conform to body contours.
A persistent problem with traditional absorbent products, especially feminine napkins, is that they are molded to the anatomy by pressure of the body and pressure from the panty. When the wearer pulls up her undergarment with the pad attached, pressure is put onto the pad when it comes in contact with the body. When the wearer sits down, her body weight forces the product to conform to her body shape. The absorbent filler, which is normally ground wood pulp, is forced to shift because of its loose structure of short fibers. When the pad is compressed to the shape by the body, the pulp yields and distorts in many directions. Such distorting can cause the pad to move off center or to either side thereby compromising its function as a fluid absorbent. The distorting, shifting pad is poorly fitting and incorrectly placed. The misplacement of the pad results in misalignment with the source of the fluid discharge and causes early product failure.
The recognition that the function of absorbent products is compromised by unwanted movement of the pad prompted the development of form-fitting absorbent products. For example, U.S. Pat. No. 4,804,380, issued Feb. 14, 1989, in the name of Lassen, et al., discloses a catamenial device having a length greater than about seven inches and having a fold at its longitudinal center of the back one-half to two-thirds of the device. The peak like shape of the back portion is said to mold to the perineum and the buttocks.
European Patent Application Publication No. 0 405 403 A2, discloses a panty-liner having at least one longitudinal fold which allows an adaptation of the width of the liner. The design allows adjustment of the width of the liner to conform to the width of the crotch of the panty.
U.S. Pat. No. 2,331,355, issued Oct. 12, 1943, in the name of Herman Strongson, discloses a catamenial pad having extra thickness at the central longitudinal portion. The central portion of the pad is gathered upwardly, and held in position by horizontal stitching through the base.
U.S. Pat. No. 2,747,575, issued May 29, 1956, in the name of Berton Mercer, discloses a catamenial pad having a longitudinal medial portion bulged to form a hump.
U.S. Pat. No. 4,573,990, issued Mar. 4, 1986, in the name of Hiroaki Ohsaki, discloses a disposable diaper being folded along its longitudinal center line into a generally inverted .OMEGA.-shaped vertical cross sectional configuration.
U.S. Pat. No. 4,595,392, issued Jun. 17, 1986, in the names of Johnson and Lassen, discloses an interlabial pad having a cylindrodially-shaped central portion. The pad is formed by folding a pad blank along the central longitudinal axis and gathering and attaching the blank below the fold line to form a cylindrodially shaped center with radial flaps.
U.S. Pat. No. 4,655,759, issued Apr. 7, 1987, in the name of Romans-Hess, et al., discloses a catamenial pad with embossed channels adjacent to the longitudinal edges of the napkin to reduce side leakage.
U.S. Pat. No. 4,701,177, issued Oct. 20, 1987, in the name of Ellis, et al., discloses an absorbent pad shaped generally in an hourglass configuration with a middle portion somewhat thicker than the absorbent portions at the ends of the pad. The pad is provided with upstanding side portions in the middle of each long edge where the absorbent is narrower.
U.S. Pat. No. 4,790,838, issued Dec. 13, 1988, in the names of Pigneul and Ruppel, discloses a device for forming a sanitary pad having a central biconcave area of reduced width.
U.S. Pat. No. 4,897,084, issued Jan. 30, 1990, in the names of Ternstrom and Lundahl, discloses an absorbent article having elastic threads arranged in a V-shaped pattern, wherein the V-shaped patterns diverge from the center of one end of the article to the corners of the article at its opposite end, thereby forming a basin or pocket which extends along the whole length of the article.
U.S. Pat. No. 4,935,021, issued Jun. 19, 1990, in the names of Huffman and Pieniak, discloses a disposable diaper having a center gathering means for providing a longitudinal gathering force.
U.S. Pat. No. 5,057,096, issued Oct. 15, 1991, in the name of Frances Faglione, discloses a genital vulva pad/sanitary napkin wherein the vulva pad member is dimensioned and configured to fit inside a woman's vulva and releasably secured to the sanitary napkin by flexible tangs.
U.S. Pat. No. 5,127,911, issued Jul. 7, 1992, in the name of Eva Baharav, discloses a sanitary napkin having a mechanism comprising a string means which allows a user the option of forming a contoured projection in the napkin by drawing together part of the longitudinal edges of the napkin so as to form a labial feminine pad to be interposed within the labia majora of the user of the pad.
European Patent Application Publication Nos. 0 335 253 A1 and 0 335 252 A2, are directed to disposable absorbent articles having a flexure-resistant deformation. The sanitary napkins have a convex upward configuration, which configuration relies on the lateral compressive forces of the wearer's thighs to form or maintain the configuration.
It has also been suggested that the problems of unwanted movement, roping, and twisting may be overcome by fixing the pad to the undergarment more securely. U.S. Pat. No. 5,098,422, issued Mar. 24, 1992, in the name of Davis, et al., discloses an absorbent product having a semi-rigid clip means for retaining the absorbent product with respect to an undergarment.
Despite advances in absorbent products, currently available products continue to exhibit problems such as leakage attributed to unwanted movement or distortion of the pad. Accordingly, there is a need for absorbent structures designed to improve the fit of the absorbent product to the body, thereby reducing unwanted movement or misalignment which may result in leakage.
It is an object of this invention to provide prebent, anatomically shaped absorbent products that are self-aligning to maintain correct placement of the pad on the body. Such products generally have a convex shape in the approximate center portion of the body facing surface which shape allows the product to conform to the body.